Week 6: The nervous system (sensory transduction and CNS) Flashcards
What is signal transduction?
The conversion of environmental factors into neural information (i.e. action potentials).
What is mechanoreception?
pressure, body position, sound, acceleration, and gravity (e.g. Pacinian corpuscles, muscle spindles, hair cells in: the organ of Corti, semicircular canals, the utricle and saccule)
What is thermoreception?
temperature (e.g. free nerve endings in skin and core temp sensors in hypothalamus)
What is photoreception
electromagnetic waves (e.g. rod and cone cells)
What is chemoreception?
specific materials / molecules (e.g. olfactory receptors in your nose, and gustatory receptors such as taste buds)
What is nociception?
cellular damage (e.g. NK1 receptor for Substance P)
What is another word for the afferent neuron?
Sensory neuron
Describe the effect of stretch on the Pacinian corpuscle
Lamellar corpuscles (a.k.a. Pacinian corpuscles) are dendrites that are surrounded by layers (lamellae) of connective tissue.
When these are distorted by a physical pressure gradient, the dendrite membrane stretches, which opens special sodium ion channels.
Once sodium rushes in, it opens voltage-gated ion channels and the signal travels down the myelinated part of the dendrite to the soma and axon hillock. It may then trigger an AP down the axon.
What is an example of direct stimulation of sensory neuronss
Pacinian corpuscles and muscle spindles
What is the receptor potential
The magnitude of depolarisation of the membrane
Describe how sound is transduced?
Pressure waves (compressions in the medium surrounding your head) are transmitted into the fluid in the vestibular duct.
These waves vibrate the connective tissue fibres in the tectorial membrane when they match resonant frequency of the fibres. The membrane is bathed in an area of high potassium, ion concentration.
Describe how action potentials are created in hair cells
- They are modified epithelial cells.
- Cilia project from the apical side.
- The tallest cilium in each cell is the kinocilium and it is linked to the stereocilia.
- When the kinocilium is bent away from the stereocilia, K+ channels open.
- When it is bent toward the stereocilia, the channels close.
Give an example of indirect stimulus of neurons
Hair cells in the epithelium (epithelial sensory receptor cells)
What are the 4 types of information the sensory receptors and neurons must encode?
- Stimulus modality
- Stimulus location
- Stimulus intensity
- Stimulus duration
What is a stimulus modality
A sensory modality (also called a stimulus modality) is an aspect of a stimulus or what is perceived after a stimulus. How the receptor can differentiate between different types of touch for example
E.g. both Meissner’s corpuscle and Merkel discs are used to differentiate between fine touch
What is a stimulus modality
A sensory modality (also called a stimulus modality) is an aspect of a stimulus or what is perceived after a stimulus. How the receptor can differentiate between different types of touch for example
E.g. both Meissner’s corpuscle and Merkel discs are used to differentiate between fine touch
How is a stimulus location determined?
By the integrating information from several cells (e.g. the brain)
What is meant by a tonic receptor?
A receptor that adapts slowly
e.g. Meissner’s corpuscle - they are good at distinguishing size and shape of an object
What is meant by a phasic receptor?
Receptor that quickly adapts
e.g. Merkel discs are good at distinguishing texture of objects
What are the roles of glial cells?
They surround neurons and hold them in place (structural support)
They supply nutrients and oxygen to neurons (neuroglobin)
They insulate neurons from each other
They destroy pathogens and remove dead neurons (meningitis)
Name the types of glial cells in the CNS
Ependymal cells
Oligodendrocytes
Microglia
Astrocytes
Name the types of glia in the PNS
Satellite cells
Schwann cells
What is the function of oligodendrocytes in the CNS?
have a similar role to Schwann cells, but in the central nervous system
What is the function of astrocytes?
Transport nutrients
